The present invention relates to an ink-jet recording head, in which a part of a pressure generating chamber communicating with a nozzle orifice that ejects ink droplets is constituted of a vibration plate, a piezoelectric element is provided via this vibration plate, and ink droplets are ejected by displacement of the piezoelectric element. Furthermore, the present invention relates to an ink-jet recording apparatus.
With regard to the ink-jet recording head, in which a part of a pressure generating chamber communicating with a nozzle orifice that ejects ink droplets is constituted of a vibration plate, this vibration plate is deformed by the piezoelectric element to pressurize ink in the pressure generating chamber, and ink droplets are ejected from the nozzle orifice, two types of recording heads are put into practical use. One is a recording head using a piezoelectric actuator of a longitudinal vibration mode, which expands and contracts in the axis direction of the piezoelectric element, and the other one is a recording head using a piezoelectric actuator of a flexural vibration mode.
In the former one, a volume of the pressure generating chamber can be changed by abutting an end surface of the piezoelectric element against the vibration plate, and manufacturing of a head suitable to high density printing is enabled. On the contrary, there is required a difficult process in which the piezoelectric element is divided in a comb tooth shape to make it coincide with an array pitch of the nozzle orifices and work whereby divided piezoelectric element is positioned and fixed to the pressure generating chamber. Thus, there is a problem of a complex manufacturing process.
On the other hand, in the latter one, the piezoelectric element can be fabricated and installed on a vibration plate by a relatively simple process in which a green sheet, which is a piezoelectric material, is adhered while fitting a shape thereof to that of the pressure generating chamber and is sintered. However, a certain size of the vibration plate is required due to use of the flexural vibration, thus there is a problem that a high density array of the piezoelectric elements is difficult.
Meanwhile, in order to solve such a disadvantage of the latter recording head, as disclosed in Japanese Patent Laid-Open (kokai)No.5-286131, a recording head is proposed, in which an even piezoelectric material layer is formed over the entire surface of a vibration plate by a deposition technology, the piezoelectric material layer is divided into a shape corresponding to the pressure generating chamber by a lithography method, and the piezoelectric element is formed so as to be independent of the others for each pressure generating chamber.
In the ink-jet recording head as described above, there is a problem that the piezoelectric element is broken due to moisture and the like in the atmosphere. In order to solve this problem, a structure is proposed, in which the piezoelectric element is sealed in a specified space to be shielded from the atmosphere, and an inert fluid is enclosed in the space to prevent destruction of the piezoelectric element.
However, such a process where the piezoelectric element is sealed in the specified space and the inert fluid is filled in the space has problems that it is relatively difficult and that a manufacturing cost thereof is increased.
Moreover, though the destruction of the piezoelectric element can be prevented also by providing humidity absorbent in the space where the piezoelectric element is sealed in place of the inert fluid, there is a problem that a manufacturing process thereof is difficult similarly to the case of the inert fluid. Furthermore, there is also a problem that a function of the humidity absorbent is lowered with the elapse of time to cause a malfunction thereof,
In consideration of circumstances as described above, the object of the present invention is to provide an ink-jet recording head capable of preventing the destruction of the piezoelectric element relatively readily and securely, and to provide an ink-jet recording apparatus.
A first aspect of the present invention for solving the above-described problems is an ink-jet recording head including a passage-forming substrate having a pressure generating chamber communicating with a nozzle orifice defined therein and a piezoelectric element provided on a region of the passage-forming substrate via a vibration plate, the region corresponding to the pressure generating chamber, comprising: a sealing member defining a piezoelectric element holding portion securing a space not to hinder a movement of the piezoelectric element, the sealing member being joined onto a side of the piezoelectric element of the passage-forming substrate; and at least one sealed portion as a space provided in a member other than the sealing member, communicating with the piezoelectric element holding portion and shielded from outside air.
In the first aspect, since a volume of the space sealing the piezoelectric element is made substantially large, a permissible level for a variation factor during a manufacturing process is increased, so that the manufacturing process can be simplified and the yield is improved.
A second aspect of the present invention is the ink-jet recording head according to the first aspect, wherein an increase in humidity in the piezoelectric element holding portion is prevented by the sealed portion.
In the second aspect, the destruction of the piezoelectric element, which is caused by the moisture, can be prevented for a long period of time.
A third aspect of the present invention is the ink-jet recording head according to any one of the first and second aspects, wherein humidity absorbent is provided in the sealed portion.
In the third aspect, the inside of the piezoelectric element holding portion is maintained at low humidity by the humidity absorbent, and the malfunction of the piezoelectric element, which is caused by the moisture and the like in the atmosphere, is prevented.
A fourth aspect of the present invention is the ink-jet recording head according to the third aspect, wherein the humidity absorbent is exchangeable.
In the fourth aspect, the humidity absorbent is exchanged at specified timing, thus the inside of the piezoelectric element holding portion can be always maintained at low humidity.
A fifth aspect of the present invention is the ink-jet recording head according to any one of the first to fourth aspects, wherein a dry fluid is filled in the sealed portion.
In the fifth aspect, the inside of the piezoelectric element holding portion is maintained securely at low humidity, and the malfunction of the piezoelectric element, which is caused by the moisture in the atmosphere, is prevented.
A sixth aspect of the present invention is the ink-jet recording head according to the fifth aspect, wherein the dry fluid is an inert fluid.
In the sixth aspect, since the piezoelectric element is maintained in the inert fluid, the malfunction of the piezoelectric element, which is caused by a change of an external environment, is prevented.
A seventh aspect of the present invention is the ink-jet recording head according to any one of the first to sixth aspects, wherein a pressure in the piezoelectric element holding portion is set equal to the atmospheric pressure or higher.
In the seventh aspect, the pressure in the piezoelectric element holding portion is always made larger than the atmospheric pressure, and the moisture can be prevented from invading the inside of the piezoelectric element holding portion from an adhesive layer or the like joining the passage-forming substrate and the sealing member to each other.
An eighth aspect of the present invention is the ink-jet recording head according to the seventh aspect, wherein pressure adjusting means for adjusting the pressure in the sealed portion to be approximately equal to the atmospheric pressure is provided in a wall defining the sealed portion.
In the eighth aspect, since the pressure in the piezoelectric element holding portion is always made approximately equal to the atmospheric pressure, a stress does not occur in the vibration plate even if the atmospheric pressure is changed, and an ink ejection characteristic can always be well maintained.
A ninth aspect of the present invention is the ink-jet recording head according to the seventh aspect, wherein the dry fluid is compressed and filled in the sealed portion.
In the ninth aspect, the pressure in the piezoelectric element holding portion is always made larger than the atmospheric pressure, and the moisture can be prevented from invading the inside of the piezoelectric element holding portion from the adhesive layer or the like joining the passage-forming substrate and the sealing member to each other.
A tenth aspect of the present invention is the ink-jet recording head according to the ninth aspect, wherein the dry fluid is supplied from the sealed portion into the piezoelectric element holding portion to maintain the pressure in the piezoelectric element holding portion approximately constant.
In the tenth aspect, the pressure in the piezoelectric element holding portion is maintained approximately constant for a long period of time.
An eleventh aspect of the present invention is the ink-jet recording head according to any one of the first to tenth aspects, wherein a drive circuit for driving the piezoelectric element is provided on the sealing member, and the drive circuit is sealed by the sealed portion.
In the eleventh aspect, it is not necessary to mold the drive circuit with resin or the like, and the manufacturing process can be simplified.
A twelfth aspect of the present invention is the ink-jet recording head according to any one of the first to eleventh aspects, wherein the passage-forming substrate consists of a single crystal silicon substrate, the pressure generating chamber is formed by anisotropic etching, and respective layers of the piezoelectric element are formed by deposition and lithography methods.
In the twelfth aspect, the malfunction of the piezoelectric element consisting of thin films, which is caused by the moisture, is prevented.
A thirteenth aspect of the present invention is the ink-jet recording head according to any one of the first to eleventh aspects, wherein the passage-forming substrate is formed of ceramics, and the respective layers of the piezoelectric element are formed by either pasting of green sheets or printing.
In the thirteenth aspect, even the piezoelectric element formed by pasting of the green sheet and the like can be securely prevented from the malfunction caused by the moisture.
A fourteenth aspect of the present invention is the ink-jet recording head according to any one of the first to eleventh aspects, wherein the piezoelectric element is a longitudinal vibration type piezoelectric element expanding and contracting in an axis direction, and the longitudinal vibration type piezoelectric element having piezoelectric materials and electrode forming materials alternately stacked.
In the fourteenth aspect, even in the case of using the longitudinal vibration type piezoelectric element, the malfunction of the piezoelectric element, which is caused by the moisture, is securely prevented.
A fifteenth aspect of the present invention is an ink-jet recording apparatus comprising the ink-jet recording head according to any one of the first to fourteenth aspects.
In the fifteenth aspect, an ink-jet recording apparatus can be realized, in which printing quality and reliability are improved.
A sixteenth aspect of the present invention is an ink-jet recording apparatus including an ink-jet recording head having a passage-forming substrate with a pressure generating chamber communicating with a nozzle orifice defined therein, a piezoelectric element provided on a region of the passage-forming substrate via a vibration plate, the region corresponding to the pressure generating chamber, and a sealing member defining a piezoelectric element holding portion securing a space not to hinder a movement of the piezoelectric element, the sealing member being joined onto a side of the piezoelectric element of the passage-forming substrate, the ink-jet recording apparatus comprising: at least one sealed portion as a space provided in a member other than the sealing member, communicating with the piezoelectric element holding portion and shielded from outside air.
In the sixteenth aspect, since the volume of the space sealing the piezoelectric element is made substantially large, the permissible level for the variation factor during the manufacturing process is increased, so that the manufacturing process can be simplified and the yield is improved.
A seventeenth aspect of the present invention is the ink-jet recording apparatus according to the sixteenth aspect, wherein the sealed portion is for preventing an increase in humidity in the piezoelectric element holding portion.
In the seventeenth aspect, the destruction of the piezoelectric element, which is caused by the moisture, can be prevented for a long period of time.
An eighteenth aspect of the present invention is the ink-jet recording apparatus according to any one of the sixteenth and seventeenth aspects, wherein humidity absorbent is provided in the sealed portion.
In the eighteenth aspect, the inside of the piezoelectric element holding portion is maintained at low humidity by the humidity absorbent, and the malfunction of the piezoelectric element, which is caused by the moisture and the like in the atmosphere, is prevented.
A nineteenth aspect of the present invention is the ink-jet recording apparatus according to the eighteenth aspect, wherein the humidity absorbent is exchangeable.
In the nineteenth aspect, the humidity absorbent is exchanged at specified timing, thus the inside of the piezoelectric element holding portion can be always maintained at low humidity.
A twentieth aspect of the present invention is the ink-jet recording apparatus according to any one of the sixteenth to nineteenth aspects, wherein a dry fluid is filled in the sealed portion.
In the twentieth aspect, the inside of the piezoelectric element holding portion is maintained securely at low humidity, and the malfunction of the piezoelectric element, which is caused by moisture, is prevented.
A twenty-first aspect of the present invention is the ink-jet recording apparatus according to the twentieth aspect, wherein the dry fluid is an inert fluid.
In the twenty-first aspect, since the piezoelectric element is held in the inert fluid, the malfunction of the piezoelectric element, which is caused by the change of the external environment is prevented.
A twenty-second aspect of the present invention is the ink-jet recording apparatus according to any one of the sixteenth to twenty-first aspects, wherein pressure in the piezoelectric element holding portion are set equal to the atmospheric pressure or higher.
In the twenty-second aspect, the pressure in the piezoelectric element holding portion is always made larger than the atmospheric pressure, and the moisture can be prevented from invading the inside of the piezoelectric element holding portion from the adhesive layer or the like joining the passage-forming substrate and the sealing member to each other.
A twenty-third aspect of the present invention is the ink-jet recording apparatus according to the twenty-second aspect, wherein pressure adjusting means for adjusting the pressure in the sealed portion to be approximately equal to the atmospheric pressure is provided in a wall defining the sealed portion.
In the twenty-third aspect, since the pressure in the piezoelectric element holding portion is always made approximately equal to the atmospheric pressure, the stress does not occur in the vibration plate even if the atmospheric pressure is changed, and the ink ejection characteristic can always be well maintained.
A twenty-fourth aspect of the present invention is the ink-jet recording apparatus according to the twenty-second aspect, wherein the dry fluid is compressed and filled in the sealed portion.
In the twenty-fourth aspect, the pressure in the piezoelectric element holding portion is always made larger than the atmospheric pressure, and moisture can be prevented from invading the inside of the piezoelectric element holding portion from the adhesive layer or the like joining the passage-forming substrate and the sealing member to each other.
A twenty-fifth aspect of the present invention is the ink-jet recording apparatus according to the twenty-fourth aspect, wherein the dry fluid is supplied from the sealed portion into the piezoelectric element holding portion to maintain the pressure in the piezoelectric element holding portion approximately constant.
In the twenty-fifth aspect, the pressure in the piezoelectric element holding portion is maintained approximately constant for a long period of time.
A twenty-sixth aspect of the present invention is the ink-jet recording apparatus according to any one of the twenty-fourth and twenty-fifth aspects, further comprising: pressure detecting means for detecting the pressure in the sealed portion; and informing means for informing a user of specified information in a case where a detection result of the pressure detecting means does not satisfy a specified condition.
In the twenty-sixth aspect, since the informing means informs the user of specified information from the detection result obtained by detection of the pressure detecting means, the user can readily determine a state in the sealed portion, for example, a residual amount of the dry fluid.
A twenty-seventh aspect of the present invention is the ink-jet recording apparatus according to any one of the sixteenth to twenty-sixth aspects, further comprising: ink supplying means for supplying ink to the ink-jet recording head, the ink supplying means being detachably held thereon, wherein the sealed portion and the ink supplying means are formed integrally.
In the twenty-seventh aspect, since the sealed portion is exchanged together with the ink cartridge, it is possible to always maintain the inside of the piezoelectric element holding portion at low humidity.
As described above, in the present invention, the piezoelectric element is sealed in each piezoelectric element holding portion, and at least one sealed portion as a space communicating with the piezoelectric element holding portion and being shielded from the outside air is provided, therefore, the piezoelectric element can be sealed in a low humidity atmosphere relatively readily, and the destruction of the piezoelectric element can be prevented.